"Businesses rely on Exchange more than any other messaging solution because of its enterprise grade management and security," Microsoft said in a statement.
There are hundreds of third-party services and tools for extending and complementing Exchange, Microsoft said. "With their announcement, Google joins an existing list of email continuity providers for Exchange," the statement reads.
Google Message Continuity costs US$25 per user, per year, for new customers and $13 per user, per year, for existing Postini customers.
Currently, the service works with Exchange 2003 and Exchange 2007. Google is looking at adding Exchange 2010 in a future release.
Once signed up, Exchange administrators need to reconfigure their domain's mail exchanger record, most commonly known as MX record, so that it points to the Postini system. That way, Postini delivers incoming messages both to the on-premise Exchange server and to the Gmail cloud. A Google sync server provides continuous, bi-directional replication between Exchange and Gmail.
Postini provides several other e-mail services, such as spam and virus detection and filtering, message archiving, e-mail encryption and Web traffic security. Its system processes 3 billion e-mails every day for 21 million end users.
Google provides several tools for helping organizations move from Exchange and Outlook to the Google Apps hosted communication and collaboration suite, including Apps Migration for Exchange and Apps Migration for Outlook.
Apps competes directly against Microsoft's cloud-based Business Productivity Online Suite (BPOS), which includes hosted versions of Exchange, SharePoint, Communications Server and Live Meeting.
In its upcoming upgrade, due next year, BPOS will be renamed Office 365 and also include Office Web Apps and, in its top tier option, also the full featured Office 2010 Professional Plus.
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